1. Field of the Invention
The present invention relates to remote radiologic surveying. In particular, the present invention relates to radiologic surveys done by autonomous robots.
2. Discussion of Background
At present radiologic surveying of an area is usually done either by placing radiological instrumentation in that area to monitor the radiation levels or by manually making radiologic measurements using several standard techniques on specific surfaces in the area.
When an area is known to be contaminated, a health physicist will make measurements of background and the radiation coming from surfaces and take samples of contaminants on those surfaces for analysis. If that surface is to be decontaminated, it will be sampled periodically during the decontamination process until all traces of contaminants are removed. The sampling may be directed to random parts of the surface or may involve measurement of all parts of the decontaminated surface.
If the area is one where radioisotopes are handled routinely but contamination is not usually present, the far more common practice is to take radiological samples for measurements on a statistical basis; that is, small portions of the surfaces are sampled at random and the overall condition of the surface is inferred from the results of these measurements. Routine monitoring may also include floor surveys, where the floor is manually scanned at a rate of 1" per second using hand-held portable monitors.
Random surveys sample only a small portion of a potentially-contaminated surface. Obviously, if contamination is present in an area that is not selected for sampling, it will go undetected and can be spread by personnel moving through and about the area. Sampling typically involves wiping the surface with a paper disk and analyzing that disk for contamination, which sample is called a smear sample and which technique is called "smearing." This techniques is only capable of locating transferable or loose contamination.
In addition, when the chance of finding contamination in an area is very low, 100 percent sampling is unrealistic because of the time and labor involved. Manual scanning is labor-intensive, cumbersome and inefficient.
The problems associated with manual scanning could be largely eliminated by an automated scanning system, preferably a system that alerts personnel to the presence of contamination. Monitoring devices that provide an alarm in the presence of a hazard are known. For example, a remotely-operated system monitors a variety of hazardous conditions and enunciates the presence of a hazard in synthesized human speech (Lemelson, U.S. Pat. No. 4,455,551). Remotely-controlled devices for environmental monitoring are also available. However, all known devices require a human operator using stereoptic television cameras to direct from a remote location the activities of a vehicle. See also Silverman, et al., U.S. Pat. No. 4,709,265. Measuring radiation over 100 percent of an area using such a device is very tedious for the operator because measurements should be done no faster than approximately 1"/sec (2.5 cm/sec). There is a need for an effective and autonomous scanning system, that is, a system that measures radiation without human supervision at least until contamination is found.